DanielRicany

Hi guys. I started from scratch with my tuning on my '85. So far I've tuned everything myself with the advice from a few forum members. Everything is turning out a lot better now that it did before.

I'm running the factory timing tables and everything.

But my problem is when I'm in fourth gear until 3000 RPMs while just cruising, I get a slight buck every 2-3 seconds. It's just one buck.

Is that cam surge? If not, what is it?

Thanks!

ben73

Sounds like too much ignition advance at that point.
Where have you set the static timing?

DanielRicany

6* BTDC with EST wire disconnected. This is with stock timing tables too.

DanielRicany

Also I took it out again and noticed that when it does this I think I can see the RPMs going up when it bucks on my analog tachometer that I have.

Mark8801

Are you running an EGR?

DanielRicany

No I deleted that along with AIR and the cat.

smooth1990

If it was cam surge you wouldnt feel it as much in 4th gear and higher due to the load on the engine. Take the car out and run it in town in 2nd and 3rd, low rpm, 18-2500. If its cam surge you will feel it. The car will be bucking back and fourth!.

DanielRicany

Bucks back and fourth slightly under 2000 RPMs with light load in the lower gears.

DanielRicany

And you can feel a slight bucking in 4th at like 1000-1500 RPMs.

Rohn

Have you disabled hyway mode? It may be run too lean if in HM.

Also during cruise (low load) you may have too much spark advance(45+). Take 2 deg out of table where that occurs and blend surrounding cells.

DanielRicany

85 doesn't have highway mode. I wish it did cuz this thing sucks gas. Lol.

And okay. I'll play around with timing. I'm using the stock timing table. Is this a common problem on stock timing tables?

Rohn

If your car is not "stock" then you need to make the tune fit. I added timing just where you are experiencing issues. I went from stock table to LT4 table. That added timing at cruise big time. No issues.

Are you using stock injectors and stock FP?

tequilaboy

To combat surge, you want to take out a lot of timing to try and kill the low speed torque in the region, so that more throttle is required to produce the same road load torque.

This will help pull more air (and less exhaust) into the cylinder that is on the intake stroke while the 90 degree adjacent cylinder is in overlap.

DanielRicany

No it's far from stock haha. I am also using the stock size injectors but they are Bosch III. And my fuel pressure is at 43.5 PSI.

Thanks.

bjankuski

DanielRicany

Oh I forgot to mention. I haven't driven it under those conditions WITHOUT the ALDL cable plugged in recently, so I don't know if it will do it without the cable plugged in. Every time that I have taken it out I have been doing data logs. bjankuski mentioned in another one of my threads that the ALDL cable being plugged in will add 8* of timing advance. So could that be why it's doing it? Is the whole timing table advanced by 8*?

bjankuski

Yes, it is, that could be a contributing factor if the 8 degrees of ALDL advance is still in the tune.

DanielRicany

Okay well I took it under the same conditions without the ALDL cable plugged in a it was hardly, hardly, hardly even noticeable. I had to give 100% of my attention to it to feel something that's really not that noticeable.

Guess it's fixed

Good thing to, because I'm usually the one who fixes things that are not broken, and end up breaking other things. Lol.

Thanks guys!